Electrical machines for integration into a propulsion engine

ABSTRACT

An electrical machine includes a stator assembly coupled to an engine stator component of a propulsion engine. The stator assembly includes a stator support assembly fixedly attached to the engine stator component and a stator disposed on the stator support structure. An electrical machine shaft is coupled to an end of a shaft of the propulsion engine via an intermediate shaft member extending axially between the end of the shaft and the electrical machine shaft. A bearing support frame extends from the propulsion engine, the bearing support frame defining a bearing cavity in conjunction with the electrical machine shaft. Electrical machine bearings radially extend from the bearing support frame to rotatably contact the electrical machine shaft. A rotor attached to a rotor support structure attached to the electrical machine shaft. The rotor rotates in conjunction with the electrical machine shaft to exchange energy with the shaft of the propulsion engine.

BACKGROUND Field

The present specification generally relates to electrical machines forincorporation into gas turbine engines.

Technical Background

Incorporating an electrical machine (e.g., an electrical generator) intoa propulsion engine to generate electrical power from mechanical energygenerated by the propulsion engine may enhance the capabilities ofaircraft by eliminating the need for heavy and bulky energy storagedevices on the aircraft. For example, the electrical power generated bythe electrical machine may be used to operate an accessory propulsor(e.g., an electric fan, motor, or the like) to supplement thrustprovided via the turbine engine. Introduction of such an electricalmachine, however, may introduce challenges relating to size, weight,accessibility, and aerodynamic performance.

Summary

An electrical machine includes a stator assembly coupled to an enginestator component of a propulsion engine. The stator assembly includes astator support assembly fixedly attached to the engine stator componentand a stator disposed on a supporting surface of the stator supportstructure. The electrical machine also includes a rotor assemblyincluding a rotor support structure connected to a shaft of thepropulsion engine and a rotor attached to the rotor support structuresuch that the rotor is disposed radially inward of the stator. The rotorexchanges rotational energy with the shaft to operate as either anelectrical motor or an electrical generator.

In another embodiment, an electrical machine includes a stator assemblycoupled to an engine stator component of a propulsion engine. The statorassembly includes a stator support assembly fixedly attached to theengine stator component and a stator disposed on a supporting surface ofthe stator support structure. The electrical machine also includes arotor assembly comprising a rotor support structure directly connectedto a shaft of the propulsion engine and a rotor attached to the rotorsupport structure. The rotor is disposed radially inward of the statorsuch that the stator assembly circumferentially surrounds the rotor. Inembodiments, the rotor rotates in conjunction with the shaft to generatea power signal. In embodiments, the electrical machine receives powerfrom an external source to provide rotational energy to the shaft.

In another embodiment, an electrical machine includes a stator assemblycoupled to an engine stator component of a propulsion engine. The statorassembly includes a stator support assembly fixedly attached to theengine stator component. A stator disposed on a supporting surface ofthe stator support structure. The electrical machine also includes anelectrical machine shaft coupled to an end of a shaft of the propulsionengine via an intermediate shaft member extending axially between theend of the shaft and the electrical machine shaft. The electricalmachine also includes a bearing support frame extending from thepropulsion engine, the bearing support frame including an axial portionextending in an axial direction. The electrical machine also includeselectrical machine bearings radially extending from the axial portion ofthe bearing support frame to rotatably contact the electrical machineshaft. The electrical machine also includes a sealing member disposedaxially aft of the electrical machine bearings, the sealing memberextending from the axial portion of the bearing support frame to theelectrical machine shaft. The electrical machine also includes a rotorassembly including a rotor support structure connected to the electricalmachine shaft and a rotor attached to the rotor support structure suchthat the rotor is disposed radially inward of the stator. Inembodiments, the rotor rotates in conjunction with the shaft of thepropulsion engine via the intermediate shaft member to generate a powersignal. In embodiments, the electrical machine receives power from anexternal source to provide rotational energy to the shaft.

In another embodiment, an electrical machine includes a stator assemblycoupled to an engine stator component of a propulsion engine. The statorassembly includes a stator support assembly fixedly attached to theengine stator component and a stator disposed on a supporting surface ofthe stator support structure. The electrical machine also includes anelectrical machine shaft coupled to an end of a shaft of the propulsionengine via an intermediate shaft member extending axially between theend of the shaft and the electrical machine shaft. The electricalmachine also includes a bearing support frame extending from thepropulsion engine, the bearing support frame defining a bearing cavityin conjunction with the electrical machine shaft. The electrical machinealso includes first and second electrical machine bearings radiallyextending from the bearing support frame to rotatably contact theelectrical machine shaft. The electrical machine also includes a sealingmember disposed axially aft of the electrical machine bearings, thesealing member extending from the bearing support frame to theelectrical machine shaft. The electrical machine also includes a rotorsupport structure connected to the electrical machine shaft and a rotorattached to the rotor support structure. The rotor rotates inconjunction with the electrical machine shaft to exchange energy withthe shaft of the propulsion engine.

In another embodiment, a propulsion engine includes a core portiongenerating exhaust that travels in an axial direction and a turbinesection coupled to a shaft. The turbine section receives the exhaust andgenerates mechanical energy to rotate the shaft. The propulsion enginealso includes a turbine frame attached to the turbine section, and theturbine frame includes an outer casing coupled to the turbine sectionand an inner hub supporting the shaft via a bearing assembly comprisingan engine bearing supporting the shaft. The propulsion engine alsoincludes an electrical machine including a stator assembly comprising astator support assembly attached to the inner hub and a stator attachedto the stator support structure; an electrical machine shaft coupled toan end of the shaft via an intermediate shaft member extending axiallybetween the end of the shaft and the electrical machine shaft; a bearingsupport frame attached to the inner hub and extending radially inwardtherefrom to define a bearing cavity extending between the bearingsupport frame and electrical machine shaft; electrical machine bearingsradially extending from the bearing support frame to rotatably contactthe electrical machine shaft; and a rotor assembly. The rotor assemblyincludes a rotor support structure connected to the electrical machineshaft and a rotor attached to the rotor support structure and extendingradially inward of the stator. The rotor rotates in conjunction with theshaft via the intermediate shaft member to exchange energy with theshaft.

Additional features, advantages, and embodiments of the processes andsystems described herein will be set forth in the detailed descriptionwhich follows, and in part will be readily apparent to those skilled inthe art from that such features, advantages, and embodiments arecontemplated and considered within the scope of the disclosure, based onthe teachings disclosed hereupon.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the subject matter claimed and described herein.The accompanying drawings are provided to facilitate a furtherunderstanding of the various embodiments, and are incorporated into andconstitute a part of this specification. The drawings illustrate thevarious embodiments described herein, and together with the descriptionserve to explain the principles and operations of the subject matterclaimed and described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrativeembodiments can be understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 depicts a cross-sectional view of the propulsion engine depictedin FIG. 1 above a central axis A-A thereof, according to one or moreembodiments described herein;

FIG. 2 depicts an enlarged view of an electrical machine of thepropulsion engine depicted in FIG. 1 according to one or moreembodiments described herein;

FIG. 3 schematically depicts a sectional view of an electrical machinethat may be incorporated into the propulsion engine depicted in FIG. 1,according to one or more embodiments described herein;

FIG. 4 schematically depicts a sectional view of an electrical machinethat may be incorporated into the propulsion engine depicted in FIG. 1according to one or more embodiments described herein; and

FIG. 5 schematically depicts a sectional view of an electrical machinethat may be incorporated into the propulsion engine depicted in FIG. 1,according to one or more embodiments described herein.

DETAILED DESCRIPTION

Reference will now be made to electrical machines for integration into apropulsion engine such as a turbine engine. The electrical machinesdescribed herein may be disposed at various axial locations within thepropulsion engine (e.g., at an aft end of the propulsion engine, betweenends of a shaft a propulsion engine) to facilitate an exchange ofrotational energy between the shaft and the electrical machine. Forexample, the electrical machines described herein may include a statorassembly coupled to an engine stator component and a rotor assembly thatis connected with the shaft of the propulsion engine such that a rotorof the rotor assembly rotates in conjunction with the shaft tofacilitate an exchange of rotational energy between the rotor assemblyand the shaft. The electrical machines described herein may be operatedin a generator mode, in which rotational energy from the shaft generatesa power signal in a stator that is provided by an electrical connectorto other components of the propulsion engine or aircraft; and a motormode, in which electrical power is provided to the electrical machinefrom an external source (e.g., a power storage device disposed on theaircraft) such that the rotor alters the rotational speed of the shaft.

In embodiments, the rotor assembly may be directly or indirectlyattached to the shaft of the propulsion engine using differentattachment structures that may have differing effects on the vibrationof the shaft. For example, in embodiments, the rotor assembly includes arotor support structure directly connected to the shaft of thepropulsion engine such that the rotor assembly is supported by a bearingassembly already incorporated into the propulsion engine. In suchembodiments, the rotor support assembly may be designed to have adesired effect on the natural vibration frequencies of the shaft of thepropulsion engine. For example, in embodiments, the structure of therotor support structure is designed to alter a vibration frequency ofthe shaft. In embodiments, the electrical load of the electrical machine(e.g., via switchable coil connections in the rotor and stator) may bemodulated to controllably dampen vibrations of the shaft of thepropulsion engine to improve the long-term operability thereof.

In embodiments, the rotor assembly is indirectly attached to the shaftof the propulsion engine via an electrical machine shaft rotatablycoupled to the shaft of the propulsion engine with an intermediate shaftmember allowing axial and radial displacements of the electrical machineshaft. The electrical machine in such embodiments may be supported byits own generator bearings to protect the electrical machine fromvibrations of the shaft of the propulsion engine. Such separate shaftand bearing embodiments may also be beneficial in that the intermediateshaft member in that the intermediate shaft member may enable decouplingof the electrical machine shaft from the engine shaft to protect theengine from the electrical machine in the event of a malfunction.

In embodiments, the electrical machine may be positioned in an aftportion of the propulsion engine (e.g., proximate to a turbine rearframe). Such positioning beneficially renders the electrical machineaccessible for maintenance and repair while the propulsion engine andelectrical machine are installed an aircraft (e.g., on a wing, on afuselage, or the like). Additionally, in embodiments, the electricalmachine may be positioned within a tail cone of the propulsion engineand be directly accessible for repairs after performance of anon-invasive procedure (e.g., opening of core cowl, removal of aft skin,and removal tail cone) on the remainder of the propulsion engine. Thisway, the electrical machine may be efficiently maintained while notdisrupting operation of the other components of the propulsion engine.Additionally, various components of the electrical machine (e.g., therotor assembly and the stator assembly) may be designed to allowindependent removal thereof from the propulsion engine. Suchnon-invasive access to the electrical machine beneficially facilitatesmaintenance and repair of the electrical machine while the propulsionengine is installed on an aircraft (e.g., on a wing, a fuselage, or thelike of the aircraft).

Referring to FIG. 1, a propulsion engine 100 is schematically depicted.The propulsion engine 100 may take various forms depending on theimplementation. In the embodiments described herein, the propulsionengine 100 is a high-bypass turbofan engine. However, other types ofturbine engines are contemplated and are within the scope of the presentdisclosure. As depicted in FIG. 1, the propulsion engine 100 includes anelectrical machine 300 disposed in an aft portion 104 of the propulsionengine 100. The aft portion 104 is disposed axially downstream (e.g., ina direction parallel to a central axis A-A of the propulsion engine 100)of a core portion 220 of the propulsion engine 100. In embodiments, theelectrical machine 300 converts mechanical energy (e.g., generated fromexhaust gases generated in the core portion 220) produced by thepropulsion engine 100 into electrical energy that may be used to powerelectrical devices of the propulsion engine 100 or components disposedelsewhere on an aircraft (including components that incorporate thepropulsion engine 100). As described herein, positioning the electricalmachine 300 in the aft portion 104 of the propulsion engine 100beneficially renders the electrical machine 300 accessible formaintenance, repair, and replacement while the propulsion engine 100 isdisposed on an aircraft (e.g., on a wing or fuselage of the aircraft).The electrical machine 300 is designed to be integrated into thepropulsion engine 100 via a set of connections that may be removedwithout invasively disassembling the entirety of the propulsion engine100 (e.g., removing without detaching the propulsion engine 100 from theaircraft).

In embodiments, the electrical machine 300 may be attached to an innerhub 226 of a turbine rear frame 222 of the propulsion engine 100.Example embodiments of the structure of the electrical machine 300 aredescribed in greater detail herein. Still referring to FIG. 1, it shouldbe understood that the depicted arrangement of the propulsion engine 100is only exemplary is not intended to be limiting. For example, inalternative embodiments, the electrical machine 300 may be disposedaxially forward of the core portion 220.

Positioning the electrical machine 300 in the aft portion 104 providesaccessibility, but creates additional design considerations for thepropulsion engine 100. Exhaust gases generated via the core portion 220are at relatively high temperatures (e.g., in excess of about 700° C. ormore in various embodiments), which renders cooling the electricalmachine 300 beneficial. Additionally, the aft portion 104 of thepropulsion engine 100 may not be directly connected to an aircraftincorporating the propulsion engine 100. Given this, electrical signalsrouted to and from the electrical machine 300 are routed through thepropulsion engine 100. In embodiments, for example, the propulsionengine 100 includes an electrical system (not depicted in FIG. 1)including a plurality of electrical lines that connect the electricalmachine 300 to an electrical machine control unit (not depicted in FIG.1). In embodiments, the electrical lines are disposed within coolingducts that provide coolant (e.g., from a bypass section disposedradially outward from the core portion 220) to the aft portion 104. Inembodiments, the electrical lines are disposed externally to the coolingducts.

In embodiments, electrical machine control unit converts the powersignal generated by the electrical machine 300 (between an alternatingcurrent signal and direct current signal, or vice versa) for provisionto additional components of the propulsion engine 100 or incorporatingaircraft. In embodiments, as described in greater detail herein, theelectrical machine control unit may also provide control signals to theelectrical machine 300 to change the mode of operation thereof (e.g.,between an electrical generator mode and an electrical motor mode)and/or the load thereof to change the rotational energy exchange betweenthe electrical machine 300 and additional components of the propulsionengine 100. In embodiments, the electrical machine control unit may bedisposed in a location within the propulsion engine 100 that isdisplaced from the electrical machine 300 (e.g., axially forward of thecore portion 220), or elsewhere on the aircraft (e.g., in a pylon).

Referring still to FIG. 1, the propulsion engine 100 includes a fan 201,a low pressure compressor 202, a high pressure compressor 204, and acombustor 206, which mixes air compressed via the high pressurecompressor 204 with fuel for generating combustion gases that flowdownstream through a high pressure turbine 208 and a low pressureturbine 210 to generate pressurized exhaust. A first shaft 212 joins thehigh pressure compressor 204 to the high pressure turbine 208. A secondshaft 216 joins the low pressure turbine 210 to the fan 201 and the lowpressure compressor 202. In embodiments, the high pressure compressor204, the combustor 206, and the high pressure turbine 208 maycollectively form the core portion 220. The core portion 220 maygenerate combustion gases that are channeled to the low pressure turbine210, which in turn powers the fan 201 via the second shaft 216. The lowpressure turbine 210 may include a plurality of rows of blades thatrotate in response to the combustion gases from the core portion 220 andthereby cause the second shaft 216 to rotate, thereby powering the fan201, low pressure compressor 202, and the electrical machine 300.

The turbine rear frame 222 is disposed aft of the low pressure turbine210 (e.g., offset from the low pressure turbine 210 in an aft direction(e.g., an axial direction 272) extending parallel to the central axisA-A). The turbine rear frame 222 includes a plurality of struts 224extending between an inner hub 226 and an outer casing 228. The turbinerear frame 222 provides an exhaust flow path for exhaust flowing fromthe low pressure turbine 210. The inner hub 226 and the outer casing 228may circumferentially surround the second shaft 216 and the plurality ofstruts 224 may be distributed around the second shaft 216. Inembodiments, the plurality of struts 224 function as outlet guide vanesto straighten the exhaust airflow, which may flow over a tail cone 230to improve performance of the propulsion engine 100. It should beunderstood that the turbine rear frame 222 may include any number ofstruts 224 in any arrangement consistent with the present disclosure.

Referring still to FIG. 1, the propulsion engine 100 includes a corecowl 250 and an aft skin 252. The core cowl 250 delineates a flow pathfor air compressed by the fan 201. In embodiments, the aft skin 252 isconnected to the outer casing of the turbine rear frame 222 via a boltedconnection (not depicted). In embodiments, exhaust exits the propulsionengine 100 via an outlet 254 defined by the turbine rear frame 222, theaft skin 252, and the tail cone 230.

Referring now to FIG. 2, a detailed view of a sectional portion of theelectrical machine 300 depicted in the dashed boundary of FIG. 1 isshown. In the depicted embodiment, the electrical machine 300 includes astator assembly 302 and a rotor assembly 304. The stator assembly 302 isdirectly connected to the propulsion engine 100 via a first enginestator component 260 and a second engine stator component 270. The firstand second engine stator components 260 and 270 may vary depending onthe particular location at which the electrical machine 300 is disposedwithin the propulsion engine 100. For example, as described herein withrespect to FIG. 1, the electrical machine 300 is disposed in the aftportion 104 of the propulsion engine 100. In such embodiments, the firstengine stator component 260 may be a flow-defining structure such as theturbine rear frame 222 depicted in FIG. 1 (e.g., the stator assembly 302may be attached to the inner hub 226) and the second engine statorcomponent 270 may be another component extending radially between thesecond shaft 216 and the inner hub 226 (e.g., a turbine component suchas a bearing support structure or the like). Alternative locations ofthe electrical machine 300 are contemplated and within the scope of thepresent disclosure. For example, in embodiments, the electrical machine300 is disposed between the ends of the second shaft 216 (e.g., axiallyforward of an aft end 217 of the second shaft 216 and the turbine rearframe 222). In such embodiments, the first engine stator component 260may be another flow path-defining structure (e.g., mid turbine frame orthe like). Various points of connection between the electrical machine300 and the propulsion engine 100 are contemplated and within the scopeof the present disclosure.

The stator assembly 302 includes a stator 314 and the rotor assembly 304includes a rotor 346. In the depicted embodiment, the rotor assembly 304is disposed radially inward of the stator assembly 302 (e.g., the entirerotor assembly 304 is disposed more proximate to the second shaft 216than the stator assembly 302). In embodiments, the stator assembly 302circumferentially surrounds the rotor assembly 304, such that the rotorassembly 304 is disposed radially between the stator assembly 302 andthe second shaft 216 of the propulsion engine 100. In embodiments, theelectrical machine 300 is operated as an electrical generator convertingrotational energy of the second shaft 216 (e.g., during flight operationof the propulsion engine 100) into electrical energy that may beconveyed to other components of an aircraft. In embodiments, theelectrical machine 300 is operated as a motor to provide torque to thesecond shaft 216 (e.g., to increase operational efficiency of thepropulsion engine 100).

The inner-rotor construction of the electrical machine 300 facilitatescompactness (e.g., aerodynamic performance) and operability thereof. Forexample, the inner-rotor construction of the electrical machine 300 mayfacilitate long-term operability thereof over embodiments where thestator assembly 302 is disposed radially inward of the rotor assembly304 by reducing rotational loads imparted on the structural componentssupporting the rotor 346 during operation of the electrical machine 300.Additionally, the inner-rotor construction of the electrical machine 300depicted in FIG. 2 may facilitate the stator assembly 302 acting as ashield to prevent damaged rotor components from traveling in a radiallyoutward direction and impacting additional components of the propulsionengine 100. For example, if the electrical machine 300 malfunctions, apiece of the rotor assembly 304 may break and become disconnected fromthe second shaft 216. Such a broken component may disrupt operation ofthe propulsion engine 100 if left unimpeded. Due to the inner-rotorconstruction of the electrical machine 300, however, such broken rotorcomponents are contained within a rotor cavity 370 delineated by thestator assembly 302. Containment of debris by the stator assembly 302reduces the likelihood of electrical machine malfunction affectingoperation of other components of the propulsion engine 100 or highenergy components being released from the propulsion engine 100.Embodiments with an outer-rotor construction are contemplated and withinthe scope of the present disclosure, but may include a debris shielddisposed radially outward of the rotor assembly 304.

In the embodiment depicted in FIG. 2, the electrical machine 300 isdirectly connected to the second shaft 216 via a rotor support structure338 of the rotor assembly 304. In embodiments, the rotor supportstructure 338 includes an attachment element (e.g., a groove,protrusion, or the like, which is not depicted) that slidably engageswith a corresponding attachment element on the second shaft 216. Forexample, in embodiments, the rotor support structure 338 may slidablyengage with the second shaft 216 at an aft end 217 of the second shaft216. A locking nut (not depicted) may secure the rotor support structure338 to the second shaft 216 such that the rotor assembly 304 rotates inconjunction with the second shaft 216 to facilitate generation ofelectrical power via the rotation of the second shaft 216.

Such embodiments where the rotor assembly 304 is attached directly tothe second shaft 216 may be referred to herein as “embedded generatorembodiments.” In embedded generator embodiments, the rotor assembly 304may be supported at least in part by a bearing assembly supporting thesecond shaft 216 (e.g., an engine bearing assembly—notdepicted—supporting the aft portion 104 of the propulsion engine 100,disposed axially proximate to the turbine rear frame 222). Embeddedgenerator embodiments may be beneficial in that the electrical machine300 may function as a shaft natural frequency damper. In embodiments,components of the rotor assembly 304 (e.g., the rotor support structure338) may be structurally designed to modify a natural frequency of thesecond shaft 216 (e.g., to alter the natural vibrational frequency ofthe second shaft 216 as compared to embodiments not incorporating theelectrical machine 300). For example, in embodiments, the stiffness andvolume of the rotor support structure 338 may be selected to remove thenatural vibration frequency of the second shaft 216 from a range wherevibration of the second shaft 216 is likely to excite vibrational modesof other components of the propulsion engine 100, thereby avoidingstructural integrity issues associated with high amplitude oscillations.

In embodiments, the electrical machine 300 may be designed to variablyimpact the natural vibration frequencies of the second shaft 216 viaexternal control thereof. In the depicted embodiment, for example, theelectrical machine 300 is communicably coupled (e.g., via electricallines 336 and 342 and an electrical connection device 328, describedherein) to an electrical machine control unit 380. The electricalmachine control unit 380 may control the electrical machine 300 based onpower demand by altering the electrical load. In embodiments, theelectrical machine control unit 380 is disposed in an axially differentlocation of the propulsion engine 100 than the electrical machine 300.In embodiments, the electrical machine control unit 380 is disposed atthe same axial location as the electrical machine 100 within thepropulsion engine.

In embodiments, for example, the electrical machine control unit 380receives instructions from another component (e.g., an engine powercontrol unit) associated with the aircraft to modulate the electricalmachine load to alter the rotational energy extracted from the secondshaft 216 via rotation of the rotor 346, thereby controllably dampeningvibrations of the second shaft 216. For example, the electrical machinecontrol unit 380 may alter the electrical load of the electrical machine300 (e.g., by switching electrical connections between coils thereof offand on) in response to vibrations of the second shaft 216 being detectedin order to dampen the detected vibrations. Such electrical load controlby the electrical machine control unit 380 may occur in both a generatorworking mode and a motor working mode of the electrical machine 300.

Referring still to FIG. 2, the rotor assembly 304 further includes arotor attachment arm 340 extending axially forward from an end of therotor support structure 338. The rotor attachment arm 340 maintains therotor 346 in spaced relation to the stator 314 and second shaft 216. Inembodiments, the rotor 346 comprises a plurality of permanent magnetscircumferentially distributed about the stator 314 such that rotation ofthe rotor 346 about the stator 314 generates an AC power signal. Itshould be understood that alternative configurations for the rotor 346are envisioned depending on the implementation of the electrical machine300. For example, in embodiments, the rotor 346 may include a pluralityof electromagnets and active circuitry. Various implementations areenvisioned wherein the electrical machine 300 is configured as aninduction type generator, a switched reluctance generator, anasynchronous AC electrical machine, or any suitable type of electricgenerator.

In embodiments, the stator assembly 302 circumferentially surrounds therotor assembly 304. In embodiments, the stator assembly 302 (e.g., thestator support assembly 308, described herein) includes a plurality ofcircumferential segments that can each be individually detached from thepropulsion engine 100 to facilitate removal thereof. Such embodimentsincorporating a plurality of circumferential segments may beparticularly beneficial in embodiments where the electrical machine iscentrally disposed within the propulsion engine 100 (e.g., away from theends of the second shaft 216), as accessing the electrical machine 300for maintenance or replacement may be more time consuming in suchembodiments.

In the depicted embodiment, the stator assembly 302 is attached to thefirst and second engine stator components 260 and 270 via first andsecond connection bolts 327 and 329, respectively. The stator assembly302 includes a stator support assembly 308 holding the stator 314 in adesired position relative to the rotor 346. The stator support assembly308 includes a stator support arm 312. The stator support arm 312extends in the axial direction 272 (e.g., parallel to the second shaft216) and defines a stator support surface 313 where the stator 314 isattached to the stator support assembly 308.

In embodiments, the stator support arm 312 extends over the entirety ofthe rotor 346 in the axial direction 272 to define the rotor cavity 370extending between the stator support arm 312 and the second shaft 216.In embodiments, the stator support arm 312 comprises a length in theaxial direction 272 that is greater than that of the rotor 346. Inaddition to providing structural support to the stator 314, the statorsupport arm 312 contributes to containment of any debris associated withthe rotor assembly 304 (e.g., in conjunction with a debris shielddisposed radially outward of the stator support arm 302), therebypreventing release of high energy components outside of the propulsionengine 100. That is, the stator support arm 312 may act as a shield toprevent malfunctioning of the rotor assembly 304 from disrupting theoperation of other components of the propulsion engine 100 or to preventthe rotor assembly 304 from emitting high energy debris outside of thepropulsion engine 100. In embodiments, the stator support arm 312 is thesole containment mechanism of the propulsion engine 100 for containingsuch debris from the rotor assembly 304. That is, the inner-rotorconstruction of the electrical machine 300 may eliminate the need fordebris shields surrounding the electrical machine 300.

In embodiments, the stator support arm 312 comprises a substantiallycylindrical structure surrounding the second shaft 216. In embodiments,the substantially cylindrical structure is an integrated, continuousbody. In embodiments, the stator support arm 312 comprises a pluralityof circumferential segments, with each of the plurality ofcircumferential segments being connected to one another in order tofacilitate individual removal of each circumferential segment radiallyaway from the second shaft 216. In embodiments, the plurality ofcircumferential segments are non-continuous circumferentially. That is,in such embodiments, the stator support arm 312 may comprise gaps arounda circumference thereof.

In embodiments, electrical and fluid connections of the electricalmachine 300 are facilitated through the structure of the stator supportassembly 308. In the embodiment depicted in FIG. 2, for example, theelectrical machine 300 includes a connector support 316 extendingradially between the first engine stator component 260 and the statorsupport arm 312. In embodiments, the connector support 316 includes atleast one opening 318 for supporting an electrical connection device328. It should be understood that embodiments are also envisioned wherethe electrical machine 300 does not include the connector support 316 orwhere the connector support 316 is disposed in a different location thanthat depicted in FIG. 2. The electrical connection device 328 mayconductively connect an electrical line 336 from the stator 314 to anexternal electrical line 342. In embodiments, the connector support 316functions as a holder of the electrical connection device 328 tofacilitate electrically connecting the electrical machine 300 to othercomponents of the propulsion engine 100. In embodiments, the connectorsupport 316 comprises a plurality of openings 318 that are distributedaround the circumference of the stator support assembly 308. Anelectrical connector may extend through each one of the plurality ofopenings to facilitate provision of electrical signals generated by theelectrical machine 300 to external components. It should be understoodthat alternative locations are envisioned for the electrical connectiondevice 328. That is, the electrical connection device 328 may bedisposed along the electrical lines 336 and 342 at alternative locationsthan that depicted in FIG. 2 (e.g., axially forward of the electricalmachine 300). In such embodiments with alternative positioning of theelectrical connection device 328, the electrical machine 300 may notinclude the connector support 316.

In embodiments, the electrical machine 300 includes a cooling system 350distributing coolant to various portions of the electrical machine 300.In the depicted embodiment, the cooling system 350 includes an inletmanifold 352 and a stator manifold 354. The inlet manifold 352 receivescoolant air from portions of the propulsion engine 100 that are externalto the electrical machine 300. In embodiments, the inlet manifold 352 isa portion of or connected to another cooling duct of the propulsionengine 100. In embodiments, the inlet manifold 352 may be routed throughthe first engine stator component 260 (e.g., through one of the struts224 of the turbine rear frame 222 depicted in FIG. 1). The statormanifold 354 provides coolant to the stator 314 to maintain atemperature thereof within a suitable operating range. In embodiments,one or more of the electrical lines and the electrical connection deviceis disposed within the cooling system 350. For example, in the depictedembodiment, the electrical lines 336 and 342 extend through the statormanifold 354 and the inlet manifold 356, respectively, and areconductively connected within the stator manifold 354 via the electricalconnection device 328. Embodiments are also envisioned where electricallines are disposed outside of the cooling system 350. In embodiments,the stator support arm 312 comprises holes or openings to lead tocooling manifolds other than those depicted in FIG. 2.

In the embodiment depicted in FIG. 2, electrical and fluid connectionsvia the cooling system 350 are disposed at an aft end of the stator 314(e.g., via the connecting portion 358 of the stator manifold 354). Itshould be appreciated that alternative embodiments are contemplated andwithin the scope of the present disclosure. For example, in embodiments,the electrical line 336 may extend from an axially forward end of thestator 314, and the stator manifold 354 may extend through the statorsupport arm 312 to facilitate attachment and connection to the axiallyforward end of the stator (e.g., the stator manifold 354 may not includethe connecting portion 358 including a bend, as in the depictedembodiment). In such embodiments, the electrical connection device 328may also be disposed axially forward of the stator 314. For example, theelectrical connection device 328 may be supported within or externallyto a portion of the stator manifold 354 extending through the statorsupport arm 312 to facilitate electrical connection with the externalelectrical line 342. Such embodiments may not include the connectorsupport 316 (the depicted embodiments may also not include the connectorsupport 316). Various combinations of electrical connection and fluidcoupling structures are contemplated and within the scope of the presentdisclosure.

In embodiments, the electrical machine 300 comprises a thermal shield348. In embodiments, the thermal shield 348 does not directly attach tothe second shaft 216 but rather circumferentially surrounds the aft end217 of the second shaft 216, the stator assembly 302, and the rotorassembly 304. In embodiments, the thermal shield 348 is attached to thefirst engine stator component 260. For example, in embodiments, thethermal shield 348 is attached to the connection flange 310 of the firstengine stator component 260 via the first connection bolt 327. Inembodiments, the thermal shield 348 comprises at least two components.In embodiments, for example, the thermal shield 348 comprises a statorportion circumferentially surrounding the stator assembly 302 and arotor portion extending axially aft of the rotor 346. In embodiments,the separate portions of the thermal shield 348 may be separatelyremoved from the propulsion engine 100 to facilitate access to the rotorassembly 304 without disruption the connections of the stator assembly302.

The view depicted in FIG. 2 corresponds to a single circumferentialsection of the electrical machine 300. As such, it should be understoodthat the electrical machine 300 may include any number of the componentsdepicted in FIG. 2 distributed around the circumference of the secondshaft 216. The components depicted in FIG. 2 may also be split axially.That is, each component depicted in FIG. 2 is a continuous section(e.g., the stator support arm 312) may be split into a plurality ofsegments extending in the axial direction 272 that extend from oneanother. In embodiments, the electrical machine 300 includes a pluralityof cooling systems that are similar to the cooling system 350 depictedin FIG. 2 (e.g., having a plurality of manifolds, electrical connectors,and electrical lines extending therethrough) distributed around thecircumference thereof. Moreover, the components of the electricalmachine 300 (e.g., the stator support assembly 308, thermal shield 348,etc.) may be connected to the propulsion engine 100 at any number ofpoints along the circumference thereof. That is, the electrical machine300 may include a plurality of first and second connection bolts 327 and329 distributed around its circumference.

Having described various components of the electrical machine 300 andthe propulsion engine 100, various advantages of the structuresdescribed with respect to FIGS. 2 and 3 can now be appreciated. Forexample, referring to FIG. 1, to render the electrical machine 300entirely accessible, the tail cone 230 may be removed. After removal ofthe tail cone 230, at least a portion of the electrical machine 300 maybe removed from the propulsion engine 100. Depending on the type ofoperation being performed, all or a portion of the electrical machine300 may be removed, depending on the process followed. For example, inembodiments, the plurality of first and second connection bolts 327 and329 attaching the stator assembly 302 to the first and second enginestator components 260 and 270 may be removed to facilitate removal ofthe thermal shield 348. A connection between the rotor support structure338 and the second shaft 216 may then be loosened to facilitate removalof the rotor assembly 304 for replacement and/or maintenance. The statorassembly 302 may also be removed from the first and second engine statorcomponents 260 and 270.

In embodiments, rather than removal of the stator assembly 302, therotor assembly 304 may be removed from the second shaft 216 withoutremoval of the connections at the plurality of first and secondconnection bolts 327 and 329. The non-radially overlapping structure ofthe stator assembly 302 and rotor assembly 304 facilitates access andremoval of the rotor assembly 304 from the propulsion engine 100 withoutdisruption of the stator assembly 302, facilitating prompt and effectivemaintenance operations.

The manner with which the electrical machine 300 is positioned andconnected within the propulsion engine 100 thus facilitates access andremoval of the electrical machine 300 without removing any components ofthe propulsion engine 100 that are disposed forward (e.g., the oppositeof the axial direction 272 depicted in FIG. 2) or radially-inward of theturbine rear frame 222. Accessing the electrical machine 300 in such anon-invasive manner facilitates maintenance or replacement of variouscomponents of the electrical machine 300 while the propulsion engine 100is disposed on a wing or fuselage of an aircraft, which minimizes timethat the aircraft may be out of commission if the electrical machine 300needs repairs. Furthermore, the manner with which the electrical machine300 is connected to various components of the propulsion engine 100provides for a streamlined process for removal of the electrical machine300 from the propulsion engine 100.

Referring now to FIG. 3, a cross-sectional view of an electrical machine400 that may be integrated into a propulsion engine (such as thepropulsion engine 100 described herein with respect to FIG. 1) isschematically depicted. The electrical machine 400 may includecomponents of the electrical machine 300 described herein with respectto FIG. 2. Accordingly, like reference numerals are utilized in FIG. 3to indicate the incorporation of such like components. The electricalmachine 400 is also an embedded generator embodiment, including a rotor346 fixedly attached to the second shaft 216. The electrical machine 400includes the stator assembly 302 described with respect to theelectrical machine 300 depicted in FIG. 2. The electrical machine 400further includes a rotor assembly 402 that differs in structure from therotor assembly 304 described with respect to FIG. 3 in that the rotorassembly 402 includes a rotor support structure 404 extending axiallyforward from its point of attachment to the second shaft 216. Inembodiments, the rotor support structure 404 is connected to the secondshaft 216 at an aft end 217 of the second shaft 216 (e.g., by engagingfeatures on the second shaft 216). As depicted in FIG. 3, the rotorsupport structure 404 extends in an axially forward direction, and therotor attachment arm 340 extends axially rearward from an end of therotor support structure 404. Such axially forward extension of the rotorsupport structure 404 provides additional space rearward of theelectrical machine 400 for disposal of additional components (e.g.,coolant manifolds, oil supply lines etc.) that may be incorporated intothe electrical machine 400 and propulsion engine 100. In embodiments,the rotor support structure 404 extends only in the radial direction274.

Referring now to FIG. 4, a cross-sectional view of an electrical machine500 that may be integrated into a propulsion engine (such as thepropulsion engine 100 described herein with respect to FIG. 1) isschematically depicted. The electrical machine 500 may includecomponents of the electrical machine 300 described herein with respectto FIG. 2. Accordingly, like reference numerals are utilized in FIG. 4to indicate the incorporation of such like components. The electricalmachine 500 differs from the electrical machine 300 in that theelectrical machine 500 is not directly connected to the second shaft216, but rather indirectly thereto via an electrical machine shaft 502.The electrical machine shaft 502 is attached to the aft end 217 of thesecond shaft 216 by an intermediate shaft member 504. In embodiments,the intermediate shaft member 504 is attached to the second shaft 216such that axial and radial vibrations of the second shaft 216 are nottransferred to the electrical machine shaft 502. For example, inembodiments, the intermediate shaft member 504 comprises a quill shaftcomprising a first spline (not depicted) at a forward end 505 thereof.The first spline may be inserted into an opening at the aft end 217 ofthe second shaft 216 to rotationally couple the second shaft 216 and theelectrical machine shaft 502. A second spline (not depicted) at an aftend 507 of the intermediate shaft member 504 may be inserted into aconnection end 503 of the electrical machine shaft 502. Such splinecouplings between the electrical machine shaft 502 and the second shaft216 may permit axial and radial movement of the electrical machine shaft502 relative to the second shaft 216 such that the electrical machine500 does not alter the natural vibration frequencies of the second shaft216. In embodiments, rather than a quill shaft, the intermediate shaftmember 504 may include a bellows spring member permitting relative axialand radial movement of the electrical machine shaft 502 relative to thesecond shaft 216. In embodiments, the intermediate shaft member 504includes a shear section that is structured to decouple (e.g., rupture)when placed under a predetermined shear load. In embodiments, theintermediate shaft member 504 and the electrical machine shaft 502 maybe integrated into a single component.

The electrical machine shaft 502 is radially supported via a generatorbearing assembly 516 attached to the second engine stator component 270via a bolted connection 552. The generator bearing assembly 516 includesa bearing support frame 514 extending radially between the electricalmachine shaft 502 and the second engine stator component 270. Asdepicted, the bearing support frame 514 includes an axial portion 518defining a bearing cavity 520 in conjunction with the electrical machineshaft 502. First and second bearing support arms 519 and 521 extend fromthe bearing support frame 514 in the axial direction 272. A firstgenerator bearing 522 extends between the first bearing support arm 519and a first portion of the electrical machine shaft 502 and a secondgenerator bearing 524 extends between the second bearing support arm 521and a second portion of the electrical machine shaft 502 to rotatablycontact the electrical machine shaft 502 (e.g., inner races connected tothe electrical machine shaft 502 may house the first and secondgenerator bearings 522 and 524 to provide such rotatable contact). Thefirst and second generator bearings 522 and 524 may include varioustypes of bearings (e.g., ball bearings, roller bearings, or the like)depending on the implementation. The first and second generator bearings522 and 524 protect the electrical machine 500 from radial and axialmovements of the second shaft 216.

FIG. 4 also depicts an engine bearing assembly 538 associated with thepropulsion engine 100. For example, in embodiments, the engine bearingassembly 538 may support the second shaft 216 via the second enginestator component 270 (e.g., the second engine stator component 270 mayinclude a support structure extending radially inward of the inner hub226 of the turbine rear frame 222). The engine bearing assembly 538includes an engine bearing support arm 540 extending from the secondengine stator component 270. The engine bearing support arm 540 definesan engine bearing cavity 541 in conjunction with the second shaft 216.An engine bearing 542 is disposed within the engine bearing cavity 541and extends between the engine bearing support arm 540 and the secondshaft 216. The engine bearing 542 rotatably contacts the second shaft216 such that the second engine stator component 270 supports the secondshaft 216.

The electrical machine 500 is thus supported by dedicated bearings(e.g., the first and second generator bearings 522 and 524) on theelectrical machine shaft 502 to protect the electrical machine 500 fromvibrations of the second shaft 216. In embodiments, the engine bearingcavity 541 and the bearing cavity 520 are fluidly isolated one anotherto mitigate the risk contamination of the engine bearing assembly 538during maintenance of the electrical machine 500. For example, in theembodiment depicted in FIG. 4, the generator bearing assembly 516includes a first sealing member 526 extending between the first bearingsupport arm 519 and the electrical machine shaft 502 and a secondsealing member 528 extending between the second bearing support arm 521and the electrical machine shaft 502. The first and second sealingmembers 526 and 528 may be constructed of a suitable compliant material(e.g., labyrinth air seals) to generate seals at the interfaces betweenthe first and second sealing members 526 and 528 and the electricalmachine shaft 502.

The engine bearing assembly 538 further comprises a sealing member 544disposed between the engine bearing support arm 540 and the second shaft216. The sealing member 544 generates a seal at the interface between itand the second shaft 216. The sealing member 544 is disposed axiallybetween the engine bearing 542 and the generator bearing assembly 516such that the engine bearing assembly 538 is fluidly isolated from thegenerator bearing assembly 516. Such isolation of the bearing assembliesfacilitates provision of lubricant from separate sources to reduce therisks of contamination during maintenance. For example, in the depictedembodiment, the propulsion engine 100 comprises an engine bearinglubrication system 546 and a generator bearing lubrication system 530.The generator bearing lubrication system 530 includes an oil supply line531 supported by the bearing support frame 514. In embodiments, the oilsupply line 531 extends through an opening in the axial portion 518 intothe bearing cavity 520. The generator bearing lubrication system 530further includes an oil ejection nozzle 532 including outlets disposedproximate to the first and second generator bearings 522 and 524 suchthat oil from a lubricant source (not depicted) travels through the oilsupply line 531 and is ejected onto surfaces of the first and secondgenerator bearings 522 and 524 to provide lubrication and cooling duringoperation thereof. The generator bearing lubrication system 530 alsoincludes an oil scavenge 534 facilitating circulation of oil out of thebearing cavity 520.

The engine bearing lubrication system 546 includes an oil supply line548 and an oil ejection nozzle 550 including an outlet disposedproximate to the engine bearing 542 to provide lubrication duringoperation thereof. By utilizing separate bearing lubrication systems(e.g., separate oil supply lines 531 and 548) to provide lubricant tothe generator bearing assembly 516 and the engine bearing assembly 538,the embodiment depicted in FIG. 4 mitigates the risks associated withperforming maintenance on the electrical machine 500.

While the depicted embodiment incorporates a generator bearinglubrication system 530 and an engine bearing lubrication system 546 thatare oil-based, it should be understood that alternative lubricationsystems using different types of lubricants are contemplated and withinthe scope of the present disclosure. Various types of fluid-basedlubricants (e.g., synthetic polymer-based lubricants), gas-basedlubricants, or solid lubricants may also be used in accordance with thepresent disclosure. Isolating the separate lubrication systemsassociated with the generator and engine bearings generally avoidscomplications in the engine bearing assembly resulting from maintenanceof the electrical machine 500, thereby avoiding disrupting operation ofthe remainder of the propulsion engine 100.

Referring still to FIG. 4, the electrical machine 500 further differsfrom the electrical machine 300 described herein with respect to FIG. 2in that the electrical machine comprises a rotor assembly 506 thatdiffers in structure from the rotor assembly 304 described herein. Therotor assembly 506 comprises a rotor support structure 508 that isattached to the electrical machine shaft 502 via a mounting flange 510of the electrical machine shaft 502. The rotor support structure 508 isattached to the mounting flange 510 by a connecting bolt 512 extendingthrough the mounting flange 510 and the rotor support structure 508. Therotor support structure 508 extends from the electrical machine shaft502 and the rotor attachment arm 340 extends axially therefrom tosupport the rotor 346 in a desired position. In embodiments, the rotorsupport structure 508 extends diagonally from the electrical machineshaft 502 (e.g., similar to the rotor support structures 338 and 404described herein with respect to FIGS. 2 and 3).

In the depicted embodiment, the rotor 346 is disposed radially inward ofthe stator assembly 302. As discussed herein, such inner rotor designfacilitates independent removal of the rotor assembly 506. Because themounting flange 510 of the electrical machine shaft 502 is disposedaxially aft of the bearing support frame 514, the connecting bolt 512may be accessed without removal of the bearing support frame 514, whichallows removal of the rotor assembly 506 independently from the statorassembly 302. Additionally, due to the inner-rotor construction of theelectrical machine 500, the stator support arm 312 may act as a debrisshield for containing any broken components of the rotor assembly 506.It should be appreciated that embodiments incorporating various aspectsof the electrical machine 500 (e.g., the electrical machine shaft 502,the intermediate shaft member 504, the generator bearing assembly 516)are also envisioned where the rotor 346 is disposed radially outward ofthe stator assembly 302.

The separate shaft coupling of the electrical machine 500 via theelectrical machine shaft 502 further facilitates separation of theelectrical machine 500 from the propulsion engine 100 by decoupling theintermediate shaft member 504. As depicted in FIG. 4, the propulsionengine 100 includes a decoupling device 536 extending from the secondengine stator component 270. The decoupling device 536 axially overlapsthe intermediate shaft member 504 such that, upon activation of thedecoupling device 536, the decoupling device 536 performs an action onintermediate shaft member 504 decouple the electrical engine shaft 502from the second shaft 216 to protect the second shaft 216 frommalfunctioning of the electrical machine 500 by mechanical disconnect ofthe electrical machine 500 from the second shaft 216.

To facilitate disassembly of the electrical machine 500 from thepropulsion engine 100 via the splines of the intermediate shaft member504, the manner with which the stator assembly 302 is connected to thepropulsion engine 100 may be modified as compared with the generatorassembly 300 described herein with respect to FIG. 3. As depicted inFIG. 4, the stator assembly 302 is not directly connected to the secondengine stator component 270, but rather to the bearing support frame514. The bearing support frame 514 is connected to the second enginestator component 270 via a first connection bolt 552, and the statorsupport arm 312 is connected to the bearing support frame 514 via asecond connection bolt 554. An axial portion 556 of the bearing supportframe 514 extends between the first and second connection bolts 552 and554 to axially separate the stator support arm 312 from the secondengine stator component 270. In embodiments, the first connection bolt552 may be detached to facilitate removal of the electrical machineshaft 502 from the intermediate shaft member 502 via the splinedconnection. Thus, the spline coupling provided by the intermediate shaftmember 504 facilitates removal of the entire electrical machine 504(e.g., the electrical machine shaft 502, the bearing support frame 514,the generator bearing assembly 516, the rotor assembly 506, and thestator assembly 302) as a single module to reduce the risk ofcontamination. After removal of the electrical machine 500, theintermediate shaft member 502 may be removed as well.

In embodiments, the second connection bolt 554 may be loosened tofacilitate removal of the stator assembly 302 without using thedecoupling device 536 (e.g., removal of the connection bolts 327, 554,and 512 may facilitate removal of the rotor assembly 506 and statorassembly 302 from the propulsion engine 100 independently of the bearingsupport frame 514). As such, the depicted design facilitates flexibilityin the operations that may be performed to remove the electrical machine500 (or portions thereof) from the propulsion engine 100. Inembodiments, the bearing support frame 514 and stator support arm 312may be structured from different materials for desired function anddurability. In embodiments, the stator support arm 312 and the bearingsupport frame 514 are integrated into a single part.

Referring now to FIG. 5, a cross-sectional view of an electrical machine600 that may be integrated into a propulsion engine (such as thepropulsion engine 100 described herein with respect to FIG. 1) isschematically depicted. The electrical machine 600 may includecomponents of the electrical machine 500 described herein with respectto FIG. 5. Accordingly, like reference numerals are utilized in FIG. 5to indicate the incorporation of such like components. The electricalmachine 600 differs from the electrical machine 500 described hereinwith respect to FIG. 4 in that the electrical machine 600 includes agenerator bearing assembly 602 and an engine bearing assembly 604 thatare disposed in a common sump 640 defined at least in part by thebearing support frame 514 and the second engine stator component 270. Asdepicted in FIG. 5, the generator bearing assembly 602 includes thefirst and second generator bearings 522 and 524 described with respectto FIG. 4, but only includes a single generator bearing sealing member622 disposed axially aft of the second generator bearing 524. The enginebearing assembly 604 includes the engine bearing 542 described withrespect to FIG. 4, but includes a single engine bearing sealing member606 disposed axially forward of the engine bearing 542. The sealingmembers 622 and 606 seal off the common sump 640 to contain lubricantsupplied to the bearings.

In the electrical machine 600, the common sump 640 is not sealed axiallybetween the first and second generator bearings 522 and 524 and theengine bearing 542. That is, the bearing cavity 520 and the bearingcavity 541 described with respect to FIG. 4 are not fluidly isolatedfrom one another. Such lack of sealing between the bearings allows acommon lubrication source to be used to lubricate the first and secondgenerator bearings 522 and 524 and the engine bearing 542. For example,in the depicted embodiment, a bearing lubrication system 608 is used tosupply lubricant to the engine bearing 542 and the first and secondgenerator bearings 522 and 524. The bearing lubrication system 608includes an oil supply line 610 extending into the coolant cavity 562from a lubricant source (not depicted). The oil supply line 610 branchesinto a generator portion 614 extending axially aft into the bearingcavity 520 and an engine portion 612 extending axially forward into thebearing cavity 541. An oil nozzle 618 at an end of the generator portion614 includes outlets providing oil to the first and second generatorbearings 522 and 524. An oil nozzle 620 disposed at an end of the engineportion 612 includes an outlet for supplying oil to the engine bearing542. The bearing lubrication system 608 further includes one or moredrain passages 626 disposed proximate to each of the bearings 522, 524,and 542 for receiving oil after the oil has been applied to the bearings522, 524, and 542. Embodiments may incorporate drain passages in theportion of the second engine stator component 270 disposed proximate tothe decoupling device 536. The drain passages 626, 628, 630 may drainthe oil near the bearings 522, 524, and 542 into the common sump 640. Ascavenge 624 may route oil to a scavenge line for filtration and reuse.

The common sump 640 of the electrical machine 600 thus facilitatesutilization of one bearing lubrication system 608 (e.g., including asingle oil supply line 610 from a lubrication source), and includes asimpler structure than the multiple lubrication systems (e.g., thegenerator bearing lubrication system 530 and the engine bearinglubrication system 546) associated with the electrical machine 500described with respect to FIG. 4. The reduction in oil lines, seals, andconnections in the electrical machine 600 may reduce the weight andcomplexity of the electrical machine 600 over the electrical machine 500described with respect to FIG. 4.

In view of the foregoing description, it should be appreciated that anelectrical machine may be integrated into a propulsion engine of anaircraft. A stator assembly of the electrical machine may be coupled toone or more engine stator components of the propulsion engine, while therotor assembly may be coupled directly or indirectly to a shaft of thepropulsion engine to facilitate an exchange of rotational energy betweenthe shaft and the electrical machine. The rotor assembly may either bedirectly connected to the shaft by a rotor support structure attached tothe shaft or indirectly connected to the shaft via an intermediate shaftmember and an electrical machine shaft. In such embodiments, theelectrical machine may be supported on its own bearings to protect theelectrical machine from vibrations of the shaft and protect the shaftfrom vibrations of the electrical machine. The electrical machine mayalso be removed in its entirety by a splined connection with theintermediate shaft member to avoid risks of magnetic contamination ofthe electrical machine during maintenance. The electrical machine may beconstructed and positioned to facilitate relatively easy access andremoval thereof to facilitate maintenance while the propulsion engine isinstalled on an aircraft.

As used herein, the term “about” means that amounts, sizes,formulations, parameters, and other quantities and characteristics arenot and need not be exact, but may be approximate and/or larger orsmaller, as desired, reflecting tolerances, conversion factors, roundingoff, measurement error and the like, and other factors known to those ofskill in the art. When the term “about” (or “substantially” or“approximately”) is used in describing a value or an end-point of arange, the specific value or end-point referred to is comprised. Whetheror not a numerical value or end-point of a range in the specificationrecites “about,” two embodiments are described: one modified by “about,”and one not modified by “about.” It will be further understood that theendpoints of each of the ranges are significant both in relation to theother endpoint, and independently of the other endpoint. For example,the approximating language may refer to being within a 1, 2, 4, 10, 15,or 20 percent margin in either individual values, range(s) of valuesand/or endpoints defining range(s) of values.

Directional terms as used herein—for example up, down, right, left,front, back, top, bottom—are made only with reference to the figures asdrawn and are not intended to imply absolute orientation.

Unless otherwise expressly stated, it is in no way intended that anymethod set forth herein be construed as requiring that its steps beperformed in a specific order, nor that with any apparatus specificorientations be required. Accordingly, where a method claim does notactually recite an order to be followed by its steps, or that anyapparatus claim does not actually recite an order or orientation toindividual components, or it is not otherwise specifically stated in theclaims or description that the steps are to be limited to a specificorder, or that a specific order or orientation to components of anapparatus is not recited, it is in no way intended that an order ororientation be inferred, in any respect. This holds for any possiblenon-express basis for interpretation, comprising: matters of logic withrespect to arrangement of steps, operational flow, order of components,or orientation of components; plain meaning derived from grammaticalorganization or punctuation, and; the number or type of embodimentsdescribed in the specification.

As used herein, the singular forms “a,” “an” and “the” comprise pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to “a” component comprises aspects having two or moresuch components, unless the context clearly indicates otherwise.

Further aspects of the invention are provided by the subject matter inthe following clauses:

1. An electrical machine comprising: a stator assembly coupled to anengine stator component of a propulsion engine, the stator assemblycomprising: a stator support assembly fixedly attached to the enginestator component; and a stator disposed on a supporting surface of thestator support structure; and a rotor assembly comprising a rotorsupport structure connected to a shaft of the propulsion engine and arotor attached to the rotor support structure such that the rotor isdisposed radially inward of the stator, wherein the rotor exchangesrotational energy with the shaft to operate as either an electricalmotor or an electrical generator.

2. The electrical machine of any preceding clause, wherein the statorassembly circumferentially surrounds the rotor assembly such that therotor assembly is disposed radially between the shaft and the statorassembly.

3. The electrical machine of any preceding clause, wherein the statorsupport assembly comprises a stator support arm extending in an axialdirection parallel to the shaft, the stator support arm defining thesupporting surface, wherein the stator support arm is at least as longas the rotor assembly in the axial direction such that an entirety ofthe rotor assembly is disposed in a rotor cavity delineated by thestator support arm and the stator support arm shields the propulsionengine from the rotor assembly.

4. The electrical machine of any preceding clause, further comprising:an electrical connection device coupled to the stator support assembly;and an electrical line extending from the stator to the electricalconnection device.

5. The electrical machine of any preceding clause, further comprising anelectrical machine control unit, the electrical machine control unitbeing electrically connected to the stator via the, wherein theelectrical machine control unit is configured to switch operation of theelectrical machine between a generator mode to generate electrical powerfrom rotation of the shaft and a motor mode in which the stator addsrotational energy to the shaft.

6. The electrical machine of any preceding clause, wherein the rotorassembly is directly connected to an end of the shaft.

7. The electrical machine of any preceding clause, wherein no portion ofthe stator assembly extends axially aft of the rotor assembly.

8. The electrical machine of any preceding clause, further comprising:an electrical machine shaft coupled to an end of the shaft of thepropulsion engine via an intermediate shaft member extending axiallybetween the shaft and the electrical machine shaft; and a generatorbearing assembly comprising: a bearing support frame extending betweenthe electrical machine shaft and the engine stator component; andgenerator bearings supporting the electrical machine shaft, wherein theelectrical machine shaft rotates within generator bearing in conjunctionwith the shaft of the propulsion shaft to rotate the rotor.

9. The electrical machine of any preceding clause, further comprising acooling system comprising one or more cooling manifolds directingcoolant from a coolant source to regions proximate to the stator and therotor.

10. An electrical machine comprising: a stator assembly coupled to anengine stator component of a propulsion engine, the stator assemblycomprising: a stator support assembly fixedly attached to the enginestator component; and a stator disposed on a supporting surface of thestator support structure; and a rotor assembly comprising a rotorsupport structure directly connected to a shaft of the propulsion engineand a rotor attached to the rotor support structure, wherein: the rotoris disposed radially inward of the stator such that the stator assemblycircumferentially surrounds the rotor, and at least one of: the rotorrotates in conjunction with the shaft to generate a power signal, andthe electrical machine receives power from an external source to providerotational energy to the shaft.

11. The electrical machine of any preceding clause, wherein the rotorsupport structure is directly connected to an end of the shaft of thepropulsion engine by a removable connection such that the rotor assemblyis independently removable from the propulsion engine.

12. The electrical machine of any preceding clause, wherein the rotorsupport structure is directly connected to the shaft between ends of theshaft of the propulsion engine.

13. The electrical machine of any preceding clause, wherein the rotorsupport structure extends in a radial and an axial direction from theend of the shaft to mechanically alter a natural vibration mode of theshaft.

14. The electrical machine of any preceding clause, further comprisingan electrical machine control unit, the electrical machine control unitbeing electrically connected to the stator, wherein the electricalmachine control unit is configured to actively modulate an electricalmachine load to influence electrical machine rotation to dampenvibrations of the shaft.

15. The electrical machine of any preceding clause, further comprising acooling system comprising one or more cooling manifolds directingcoolant from a coolant source to regions proximate to the stator and therotor.

16. The electrical machine of any preceding clause, wherein anelectrical line extending from the stator is at least partially routedthrough the one or more cooling manifolds.

17. An electrical machine comprising: a stator assembly coupled to anengine stator component of a propulsion engine, the stator assemblycomprising: a stator support assembly fixedly attached to the enginestator component; and a stator disposed on a supporting surface of thestator support structure; and an electrical machine shaft coupled to anend of a shaft of the propulsion engine via an intermediate shaft memberextending axially between the end of the shaft and the electricalmachine shaft; a bearing support frame extending from the propulsionengine, the bearing support frame including an axial portion extendingin an axial direction; electrical machine bearings radially extendingfrom the axial portion of the bearing support frame to rotatably contactthe electrical machine shaft; a sealing member disposed axially aft ofthe electrical machine bearings, the sealing member extending from theaxial portion of the bearing support frame to the electrical machineshaft; and a rotor assembly comprising: a rotor support structureconnected to the electrical machine shaft; and a rotor attached to therotor support structure such that the rotor is disposed radially inwardof the stator, wherein at least one of: the rotor rotates in conjunctionwith the shaft of the propulsion engine via the intermediate shaftmember to generate a power signal, and the electrical machine receivespower from an external source to provide rotational energy to the shaft.

18. The electrical machine of any preceding clause, wherein the rotorsupport structure is connected to the electrical machine shaft axiallyrearward of the generator bearing to facilitate removal of the rotorfrom the electrical machine shaft.

19. The electrical machine of any preceding clause, further comprising adecoupling device attached to the propulsion engine, the decouplingdevice positioned to axially overlap the intermediate shaft member todecouple the intermediate shaft member.

20. The electrical machine of any preceding clause, further comprising aseal extending between the bearing support frame and the electricalmachine shaft, the seal fluidly isolating the electrical machinebearings from bearings of the propulsion engine.

21. An electrical machine comprising: a stator assembly coupled to anengine stator component of a propulsion engine, the stator assemblycomprising: a stator support assembly fixedly attached to the enginestator component; and a stator disposed on a supporting surface of thestator support structure; and an electrical machine shaft coupled to anend of a shaft of the propulsion engine via an intermediate shaft memberextending axially between the end of the shaft and the electricalmachine shaft; a bearing support frame extending from the propulsionengine, the bearing support frame defining a bearing cavity inconjunction with the electrical machine shaft; first and secondelectrical machine bearings radially extending from the bearing supportframe to rotatably contact the electrical machine shaft; a sealingmember disposed axially aft of the electrical machine bearings, thesealing member extending from the bearing support frame to theelectrical machine shaft; a rotor support structure connected to theelectrical machine shaft; and a rotor attached to the rotor supportstructure, wherein the rotor rotates in conjunction with the electricalmachine shaft to exchange energy with the shaft of the propulsionengine.

22. The electrical machine of any preceding clause, wherein: the bearingcavity is defined by the bearing support frame in conjunction with theelectrical machine shaft, and an engine bearing of the propulsion engineis disposed within the bearing cavity.

23. The electrical machine of any preceding clause, further comprising:an oil supply line extending through the bearing support frame into acommon sump defined at least in part between the bearing support frameand the electrical machine shaft; a first oil nozzle extending from theoil supply line and disposed proximate to the electrical machinebearings; and a second oil nozzle extending from the oil supply line anddisposed proximate to the engine bearing.

24. The electrical machine of any preceding clause, wherein: the statorassembly comprises a stator support arm connected to the engine statorcomponent via an axial portion of the bearing support frame; and the oilsupply line extends through the axial portion of the bearing supportframe into the common sump.

25. The electrical machine of any preceding clause, further comprisingan engine bearing support arm connected to the second engine statorcomponent, the engine bearing support arm defining an engine bearingcavity in conjunction with the shaft of the propulsion engine.

26. The electrical machine of any preceding clause, further comprising afirst sealing member and a second sealing member extending between thebearing support frame and the electrical machine shaft to seal off thebearing cavity.

27. The electrical machine of any preceding clause, further comprising:a first oil supply line extending through the bearing support frame intothe bearing cavity; and a second oil supply line extending into theengine bearing cavity.

28. The electrical machine of any preceding clause, further comprising adecoupling device attached to the propulsion engine, the decouplingdevice axially overlapping the intermediate shaft member such that thedecoupling device decouples the intermediate shaft member uponactivation.

29. The electrical machine of any preceding clause, wherein theintermediate shaft member permits movement of the electrical machineshaft relative to the shaft of the propulsion engine in an axialdirection and a radial direction.

30. The electrical machine of any preceding clause, wherein theintermediate shaft comprises a quill shaft comprising a first splinedisposed at a first end thereof and a second spline disposed at a secondend thereof, wherein the first and second splines are inserted intoopenings at ends of the shaft of the propulsion engine and theelectrical machine shaft to permit the movement of the electricalmachine shaft in the axial and radial directions.

31 The electrical machine of any preceding clause, wherein entireties ofthe rotor and the rotor support structure are disposed radially inwardof the stator assembly.

32. The electrical machine of any preceding clause, wherein the rotorsupport structure is connected to an end of the electrical machine shaftby a removable connection such that the rotor support structure androtor are independently removable from the propulsion engine.

33. The electrical machine of any preceding clause, wherein theintermediate shaft comprises a shear section structured to decouple whenplaced under a predetermined shear load.

34. A propulsion engine comprising: a core portion generating exhaustthat travels in an axial direction; a turbine section coupled to ashaft, wherein the turbine section receives the exhaust and generatesmechanical energy to rotate the shaft; a turbine frame attached to theturbine section, the turbine frame comprising: an outer casing coupledto the turbine section; and an inner hub supporting the shaft via abearing assembly comprising an engine bearing supporting the shaft; andan electrical machine comprising: a stator assembly comprising a statorsupport assembly attached to the inner hub and a stator attached to thestator support structure; an electrical machine shaft coupled to an endof the shaft via an intermediate shaft member extending axially betweenthe end of the shaft and the electrical machine shaft; a bearing supportframe attached to the inner hub and extending radially inward therefromto define a bearing cavity extending between the bearing support frameand electrical machine shaft; electrical machine bearings radiallyextending from the bearing support frame to rotatably contact theelectrical machine shaft; and a rotor assembly comprising: a rotorsupport structure connected to the electrical machine shaft; and a rotorattached to the rotor support structure and extending radially inward ofthe stator, wherein the rotor rotates in conjunction with the shaft viathe intermediate shaft member to exchange energy with the shaft.

35. The propulsion engine of any preceding clause, wherein: the turbineframe further comprises a plurality of struts extending between theouter casing and the inner hub, and at least one of the plurality ofstruts defines an internal cavity having a cooling duct disposedtherein.

36. The propulsion engine of any preceding clause, wherein theelectrical machine further comprises a cooling system comprising astator manifold to provide coolant from a coolant source to the statorassembly and the rotor assembly.

37. The propulsion engine of any preceding clause, wherein theintermediate shaft member and the electrical machine shaft are anintegrated component.

38. The propulsion engine of any preceding clause, further comprising adecoupling device axially overlapping the intermediate shaft member suchthat the decoupling device decouples the intermediate shaft member uponactivation.

39. The propulsion engine of any preceding clause, wherein theintermediate shaft member permits movement of the electrical machineshaft relative to the shaft of the propulsion engine in an axialdirection and a radial direction.

40. The propulsion engine of any preceding clause, further comprising asealing member extending between the bearing support frame and theelectrical machine shaft to seal the bearing cavity.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus, it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An electrical machine comprising: a statorassembly coupled to an engine stator component of a propulsion engine,the stator assembly comprising: a stator support assembly fixedlyattached to the engine stator component; and a stator disposed on asupporting surface of the stator support structure; and an electricalmachine shaft coupled to an end of a shaft of the propulsion engine viaan intermediate shaft member extending axially between the end of theshaft and the electrical machine shaft; a bearing support frameextending from the propulsion engine, the bearing support frame defininga bearing cavity in conjunction with the electrical machine shaft; firstand second electrical machine bearings radially extending from thebearing support frame to rotatably contact the electrical machine shaft;a sealing member disposed axially aft of the electrical machinebearings, the sealing member extending from the bearing support frame tothe electrical machine shaft; a rotor support structure connected to theelectrical machine shaft; and a rotor attached to the rotor supportstructure, wherein the rotor rotates in conjunction with the electricalmachine shaft to exchange energy with the shaft of the propulsionengine.
 2. The electrical machine of claim 1, wherein: the bearingcavity is defined by the bearing support frame in conjunction with theelectrical machine shaft, and an engine bearing of the propulsion engineis disposed within the bearing cavity.
 3. The electrical machine ofclaim 2, further comprising: an oil supply line extending through thebearing support frame into a common sump defined at least in partbetween the bearing support frame and the electrical machine shaft; afirst oil nozzle extending from the oil supply line and disposedproximate to the electrical machine bearings; and a second oil nozzleextending from the oil supply line and disposed proximate to the enginebearing.
 4. The electrical machine of claim 3, wherein: the statorassembly comprises a stator support arm connected to the engine statorcomponent via an axial portion of the bearing support frame; and the oilsupply line extends through the axial portion of the bearing supportframe into the common sump.
 5. The electrical machine of claim 1,further comprising an engine bearing support arm connected to the secondengine stator component, the engine bearing support arm defining anengine bearing cavity in conjunction with the shaft of the propulsionengine.
 6. The electrical machine of claim 5, further comprising a firstsealing member and a second sealing member extending between the bearingsupport frame and the electrical machine shaft to seal off the bearingcavity.
 7. The electrical machine of claim 6, further comprising: afirst oil supply line extending through the bearing support frame intothe bearing cavity; and a second oil supply line extending into theengine bearing cavity.
 8. The electrical machine of claim 1, furthercomprising a decoupling device attached to the propulsion engine, thedecoupling device axially overlapping the intermediate shaft member suchthat the decoupling device decouples the intermediate shaft member uponactivation.
 9. The electrical machine of claim 1, wherein theintermediate shaft member permits movement of the electrical machineshaft relative to the shaft of the propulsion engine in an axialdirection and a radial direction.
 10. The electrical machine of claim 9,wherein the intermediate shaft comprises a quill shaft comprising afirst spline disposed at a first end thereof and a second splinedisposed at a second end thereof, wherein the first and second splinesare inserted into openings at ends of the shaft of the propulsion engineand the electrical machine shaft to permit the movement of theelectrical machine shaft in the axial and radial directions.
 11. Theelectrical machine of claim 21, wherein entireties of the rotor and therotor support structure are disposed radially inward of the statorassembly.
 12. The electrical machine of claim 1, wherein the rotorsupport structure is connected to an end of the electrical machine shaftby a removable connection such that the rotor support structure androtor are independently removable from the propulsion engine.
 13. Theelectrical machine of claim 1, wherein the intermediate shaft comprisesa shear section structured to decouple when placed under a predeterminedshear load.
 14. A propulsion engine comprising: a core portiongenerating exhaust that travels in an axial direction; a turbine sectioncoupled to a shaft, wherein the turbine section receives the exhaust andgenerates mechanical energy to rotate the shaft; a turbine frameattached to the turbine section, the turbine frame comprising: an outercasing coupled to the turbine section; and an inner hub supporting theshaft via a bearing assembly comprising an engine bearing supporting theshaft; and an electrical machine comprising: a stator assemblycomprising a stator support assembly attached to the inner hub and astator attached to the stator support structure; an electrical machineshaft coupled to an end of the shaft via an intermediate shaft memberextending axially between the end of the shaft and the electricalmachine shaft; a bearing support frame attached to the inner hub andextending radially inward therefrom to define a bearing cavity extendingbetween the bearing support frame and electrical machine shaft;electrical machine bearings radially extending from the bearing supportframe to rotatably contact the electrical machine shaft; and a rotorassembly comprising: a rotor support structure connected to theelectrical machine shaft; and a rotor attached to the rotor supportstructure and extending radially inward of the stator, wherein the rotorrotates in conjunction with the shaft via the intermediate shaft memberto exchange energy with the shaft.
 15. The propulsion engine of claim14, wherein: the turbine frame further comprises a plurality of strutsextending between the outer casing and the inner hub, and at least oneof the plurality of struts defines an internal cavity having a coolingduct disposed therein.
 16. The propulsion engine of claim 15, whereinthe electrical machine further comprises a cooling system comprising astator manifold to provide coolant from a coolant source to the statorassembly and the rotor assembly.
 17. The propulsion engine of claim 14,wherein the intermediate shaft member and the electrical machine shaftare an integrated component.
 18. The propulsion engine of claim 14,further comprising a decoupling device axially overlapping theintermediate shaft member such that the decoupling device decouples theintermediate shaft member upon activation.
 19. The propulsion engine ofclaim 14, wherein the intermediate shaft member permits movement of theelectrical machine shaft relative to the shaft of the propulsion enginein an axial direction and a radial direction.
 20. The propulsion engineof claim 14, further comprising a sealing member extending between thebearing support frame and the electrical machine shaft to seal thebearing cavity.